In the latest World Happiness Report – an update released to coincide with International Day of Happiness on March 20, just 11 months after the 2015 report came out – the United States ranks 13 among 157 countries listed in the report.

Coming in at the top at number one was Denmark, followed by Switzerland, Iceland, Norway, Finland, Canada, Netherlands, New Zealand, Australia, Sweden, Israel, Austria, and then the United States, which came in just above Costa Rica, Puerto Rico, Germany, Brazil, Belgium, Ireland, and Luxembourg to round out the top twenty.

Burundi ranked last at 157 after Syria, Togo, and Afghanistan. Others in the bottom ten include Benin, Rwanda, Guinea, Liberia, Tanzania, and Madagascar.

Editors used Gallup World Poll data of 3,000 people’s self-evaluation of subjective well-being. People from 157 countries were asked to evaluate their lives measured on a Cantril ladder scale, with 10 representing the best possible life, and 0 representing the worst over the years 2013-2015.

In the top 10 countries, life evaluations averaged 7.4 on the 0 to 10 scale, while for the bottom 10 the average is less than half that, at 3.4, according to the report.

“A difference of four points in average life evaluations, on a scale that runs from zero to ten, separates the 10 happiest countries from the 10 least happy countries,” said the report. “Three-quarters of the differences among countries, and also among regions, are accounted for by differences in six key variables, each of which digs into a different aspect of life.”

Those factors are GDP per capita, healthy years of life expectancy, social support (as measured by having someone to count on in times of trouble), trust (as measured by a perceived absence of corruption in government and business), perceived freedom to make life decisions, and generosity (as measured by recent donations).

Differences in social support, incomes and healthy life expectancy are the three most important factors, according to the report.

“All six of those variables are important and life evaluations are much more determined by those variables than are either positive effect or negative affect, but if you add positive affect to the explanation of life evaluation it strongly adds to the explanation,” said report editor John Helliwell at the Canadian Institute for Advanced Research and Vancouver School of Economics at the University of British Columbia. Respondents were also asked about their moods in the survey, used in the report to measure negative and positive affect (or emotion).

Catherine A. Sanderson, Ph.D., the Manwell Family Professor of Life Sciences for the Department of Psychology at Amherst College in Amherst, Mass., says the findings from the report are not surprising. “On the positive side, the United States is ranked pretty well globally at 13,” she said. “On the negative side, there are countries well ahead of us and happiness in the United States isn’t increasing over time.”

New to the World Happiness Report this year was a look at the distribution of happiness. Editors of the report “argue that inequality of well-being provides a better measure of the distribution of welfare than is provided by income and wealth which have thus far held [center] stage when the levels and trends of inequality are being considered,” according to the report.

Data from the report suggest a general rise in the inequality of happiness and that countries with more equal distribution of well-being had higher average life evaluations.

The first World Happiness Report came out in 2012. Future reports or updates will continue to coincide with International Day of Happiness, Helliwell said.